Accommodating intraocular lens implant

ABSTRACT

An intraocular lens assembly for implantation in a human eye, the eye including a ciliary muscle and zonules controlled by the ciliary muscle, the assembly including an optic having anterior and posterior surfaces depending from a common edge, at least two, preferably rigid, linkage arms, each being attached to the optic at a first position on the arm thereof and cooperating with ciliary muscle or the zonules at a second position on the arm, and at least two pivots, one of which is rotatably attached to each respective linkage arm intermediate the first and second positions.

FIELD OF THE INVENTION

This invention relates to an intraocular lens assembly, for implantationinto the human eye, which permits accommodation in response to thecontraction and relaxation of the ciliary muscles.

BACKGROUND OF THE INVENTION

Normally when a person focuses on an object disposed at a distance fromthe eye, focusing is achieved by virtue of the contraction of theciliary muscles which affects the curvature of the lens and thereby itsfocal length. The process whereby the eye is able to focus on objectsover a wide range of distances from the eye is called "accommodation".It is known, during cataract operations, for example, to remove materialfrom the lens capsule and replace it by an intraocular lens implant. Thesimplest of such implants are fixed lenses having a single focal length.Such lenses do not provide for any accommodation by the eye for thedistance of objects and therefore are of relatively limited utility.

An improved type of lens for implantation provides a number of focallengths. Some of the light impinging the lens is subjected to focusingat each of the different focal lengths of the lens. This type of lensdoes provide for a broader range of focus for the eye. Only a portion ofthe light, however, is focused on the retina of the eye for any of thefocal lengths. Thus, if an object is focused by one of the focallengths, only 25-50% of the light will be focused, the remainder will beonly partly focused or unfocused. This results in a reduction ofcontrast of the focused object and a reduction in visual acuity.

A number of proposals have been made for changing the focal length ofthe lens in response to the natural accommodation mechanism of the eye.While these adaptive lens proposals exist on paper, none of them arecommercially available and, as far as is known to the applicant, nonehave been reported as having been implemented in humans.

One type of adaptive lens comprises an artificial lens whose shape ischanged in response to the contraction and expansion of the ciliarymuscle. This type of lens is proposed in U.S. Pat. Nos. 4,842,601 toSmith, 4,888,012 to Horn et al. and 4,253,199 to Banko.

Two other types of adaptive lenses are described in U.S. Pat. No.4,994,082 to Richards et al. Some embodiments described in this patentcomprises one or two lenses whose position in the plane perpendicular tooptic axis of the eye is adjusted by a mechanical structure effected bythe ciliary muscle of the eye. A second type of embodiment utilizes twolenses (comprising a compound lens) whose spacing along the optical axisis adjusted to change the focal power of the compound lens. U.S. Pat.No. 5,275,623 to Sarfarazi show a similar type of compound adaptivelens. U.S. Pat. No. 4,892,543 to Turley describes a compound systemcomprising a fixed lens having curved posterior and anterior surfacesand a second component which is positioned axially posterior of thelens. During accommodation, the movable component is forced against theposterior surface of the lens. The movement and subsequent distortion ofthe movable portion results in a change in the focal power of thecompound lens.

U.S. Pat. Nos. 4,790,847 to Woods, 5,152,789 to Willis, 4,409,691 toLevy and 4,254,509 to Tennant describe adaptive lens systems utilizing asimple intraocular lens. These systems have focusing capabilities whichare achieved by axially shifting the lens in response to normalcontraction and expansion of the ciliary muscle resulting from changesin range between the eye and an object under observation. These patents(and the Turley and Richards et al. patents) describe similar systemsfor providing motion of the lens. In each case the ciliary musclecontrols zonules, which in turn provide tension to a lens capsule inwhich the lens system is mounted. The extremities of the capsule pressagainst a radially compelled, spring-like structure which also forms arelatively large angle of somewhat less than 90° with the optical axisof the eye. The lens is positioned on the optical axis. Relaxation ofthe ciliary muscle releases the radial force and allows the spring toform a more nearly flat shape. When the ciliary muscle contracts, thepressure on the spring is increased by the action of the lens capsule,the angle between the spring and the optical axis is decreased, and thelens moves axially away from the ciliary muscle. This causes an increaseof the offset of the lens from the plane of the ciliary muscle. Themovement of the lens changes the position of the lens vis-a-vis theretina resulting in accommodation of the eye for the distance of aviewed object.

The bias of the lens with respect to the eye is different for thevarious patents, with Tennant, Willis, Turley and Levy having the lensbiased toward the posterior of the eye and Woods having the lens biasedtoward the anterior of the eye.

The theory on which Woods bases his approach is that of the classicalHelmholtz hypothesis of accommodation, in accordance with which when theeye is focused for far vision, the ciliary muscle relaxes and the lenscapsule assumes a more discoid shape. This occurs because theextremities of the lens capsule are attached via the zonular fibers tothe ciliary muscle. According to Helmholtz, contraction of the ciliarymuscle reduces tension in the zonular fibers whilst relaxation of theciliary muscle has the reverse effect.

In the Woods patent the system includes an optic (lens) and at least tworearwardly extending haptics which bear against the circumference of thelens capsule and are so formed that the lens bears against the anteriorwall of the lens cavity when the ciliary muscle is contracted, thusadjusting for correct near vision.

Woods provides a very detailed resume of the relevant prior art and,rather than describe the techniques which have been used for intraocularimplant, the reader is referred to the Woods patent which isincorporated herein by reference.

U.S. Pat. No. 4,409,691 to Levy is also based on the Helmholtz model butuses a different arrangement to provide accommodation. In Levy, theoptic is provided with a pair of radially extending struts which aremolded integrally with the optic and are just long enough so that theirrespective terminations are in light pressure contact with the perimeterof the lens capsule when the optic is implanted in the eye, the ciliarymuscle then being relaxed. The optic itself bears against the posteriorcavity wall and provides correct focus for far vision.

In Levy the capsule is controlled by the ciliary muscle itself and notby the zonules, which may, in fact, be removed and replace by a softcushion in one of his embodiments. In accordance with the Helmholtzhypothesis, the ciliary muscle contracts as the eye tries to focus on anearby object, it drives the outer end of the struts radially inwardly,thereby forcing the optic forwardly, away from the fovea centralis andincreasing the optic-to-image distance. This allows the eye to focus onrelatively near objects.

When the eye tries to focus again on far objects, the ciliary musclerelaxes, the extremities of the lens capsule move radially outward andthe compressive force bearing on the struts is reduced, allowing theoptic to move further back toward the posterior cavity wall.

Both Woods and Levy are based on the same principle, namely the movementof the lens away from the fovea during accommodation when the ciliarymuscle contracts. In Woods, the haptics are constructed such that thecontraction of the ciliary muscle causes the lens to be forced againstthe anterior wall of the lens capsule while in Levy the struts are soconstructed that the lens is moved away from the fovea by the posteriorwall of the lens capsule.

Recent research, however, indicates that the Helmholtz hypothesis ofaccommodation for near vision may be incorrect. Specifically, Ronald A.Schachar reports in Ann. Ophthal. 1992; 24:445-452 that, duringaccommodation, contraction of the ciliary results in an increase inzonular tension. Thus, according to Schachar, "the equatorial diameterof the lens is actually increased in contrast to Helmholtz's hypothesisand its modifications. When the ciliary muscle contracts duringaccommodation, the peripheral volume of the lens is decreased, resultingin an increase in the central volume of the lens and the optical powerof the lens". This conclusion is reiterated by Schachar in Ann. Ophthal.1993; 25:404-409 wherein he states: "Helmholtz's hypothesis ofaccommodation and its modifications state that the equatorial diameterof the lens decreases during accommodation. In contradiction, Schachar'shypothesis asserts that the equatorial diameter of the lens increaseswith accommodation."

Further research by Schachar, Ann. Ophthal. 1994; 26:4-9 corroborateshis hypothesis.

Consequently, the theory in accordance with which the Woods patent isbased, namely the change in tension of the zonules with accommodation,may be incorrect and the device of Woods, if one were to install it in apatient, could give reverse accommodation.

One problem which occurs with the implantation of accommodating lenseshaving a fixed focal length relates to the need to provide sufficientaxial displacement of the optic within the eye in order to providecorrect focusing throughout the complete range from near to far vision.It will be understood that the ciliary muscles themselves undergo amaximum radial displacement of approximately 200 micrometers from theirrelaxed to contracted conditions. Additionally, for a fixed focal lengthoptic, an axial displacement of approximately 1 mm is necessary to allowfor complete accommodation. In other words, the very slight radialdisplacement of the ciliary muscle must be amplified in order to allowfor complete accommodation.

Prior art patents attempt to achieve this amplification of movement byproviding haptics (or struts or other coupling elements) which form arelatively large angle with the optic axis. Th small radial movements ofthe ciliary muscle are translated into much larger movements in thedirection of the optical axis. This amplification is approximately equalto the tangent of the angle with the optical axis. This amplification isreduced, however, by inherent flexibility of the coupling elements.Moreover, such amplification is very sensitive to the angle of theelements with the optical axis, which angle itself varies with theamount of accommodation and is not well controlled.

Furthermore, no surgical adjustment is made in the prior art referencesfor locating the intraocular lens implant at precisely the correctdistance from the retina to allow for correct far or near vision. Thus,both Woods and Levy who design their optics for correct far vision,merely assume that the ciliary muscle is relaxed (as required byHelmholtz's hypothesis) and design the haptics (or struts) and optic sothat the optic is of proper strength and is properly positioned toachieve focus for distant objects when the eye is relaxed.

However, it would clearly be desirable to provide an intraocular lensimplant allowing for complete accommodation and also permitting surgicaladjustment so that the eye is correctly focused without the need forcorrection spectacles.

U.S. Pat. No. 4,575,373 to Johnson describes a non-accommodating (i.e.,non-adaptive) lens whose shape may be adjusted using an external laserwhich selectively heats a portion of the periphery of the lens andcauses the shape of the lens to change. This causes a permanent changein the focal power of the implanted lens. However, there is no teachingof how such an adjustable lens may also be made adaptive.

SUMMARY OF THE INVENTION

The present invention provides an improved method and apparatus forproviding accommodation utilizing one or more optics which move inresponse to changes in the ciliary muscle and the zonules.

These improved methods are generally characterized by improved controlover the motion of the optic and/or increased axial movement of theoptic for a given change in the tension in the ciliary muscle and thezonules.

In some embodiments of the invention this improvement is achieved byutilizing rigid haptics or linkage arms rather than resilient haptics.In other embodiments of the invention this improvement is achieved byutilizing a fulcrum and pivot structure for the haptics which act aslever arms or linkages. Some embodiments of the invention include boththese improvements.

Within the context of the invention the terms "rigid" and "flexible" or"resilient" have a special meaning. The haptics attached to the optic inprior art, such as in the Woods patent, to which reference has beenmade, are, in fact, resilient wires formed of plastics or any otherbiologically inert material. They are sufficiently stiff so that when acompressive force is applied thereto, they distort but do not buckle.Rather, they push the optic to which they are attached forward along theoptical axis. However, they are also sufficiently resilient so that whenthe compressive force is reduced, they spring back under their ownelasticity so as to return the optic toward its original position. It isthis property, namely that a compressive force applied to the lever armsdoes not cause them to buckle or otherwise collapse, which is essentialfor prior art inventions, and it is to this extent that the term"flexible, resilient" is to be understood herein.

Many preferred embodiments of the present invention, however, usesubstantially rigid elements, and in particular substantially rigidlinkage arms or haptics. These elements are considered to be rigidbecause, in these embodiments, they do not deform significantly underthe compressive or tensile forces present during accommodation. Theyare, therefore, capable of transmitting forces applied to them moreefficiently than flexible elements and potentially with greatermechanical advantage. It is in this context that the term "rigid" is tobe understood in relation to the present invention. It should beunderstood, however, that these "rigid" segments are made of very thinmaterial and may not be rigid under other circumstances, such as duringsurgical implantation, when greater force is applied to them so thatthey can be inserted into the lens capsule.

Other preferred embodiments of the present invention, however, may uselinkage arms or haptics made of flexible, resilient material, which maybe similar to the haptic materials used in Woods and other prior artpatents. Preferred embodiments of the present invention using flexible,resilient linkage arms still differ from the prior art, however, byvirtue of their use of pivot connections to convert radial motion of theciliary muscle and zonules to axial motion of the optic more efficientlyand with greater mechanical advantage.

The present invention also provides, in some embodiments thereof forimproved haptic configurations, improved methods of attachment ofhaptics to the optic and for improved methods of providing structure tothe lens capsule remaining after surgery to further increase theeffectiveness of the accommodation of the eye after lens replacement.

In yet another aspect of the invention, method and apparatus areprovided for adjusting the position of the optic during or after itsimplantation so as to provide optimum accommodation.

Furthermore, embodiments of the present invention can be designed tooperate properly in the eye regardless of whether the classicalHelmholtz theory or the new Schachar theory of accommodation is correct.

In one group of embodiments of the present invention, an intraocularlens assembly incorporates an optic for implantation within the lenscapsule of the eye, the optic being held in place by at least twosubstantially rigid linkage arms, or haptics, which are attached attheir inner ends to the edge or face of the optic. The outer ends of thelinkage arms are coupled with the movement of the zonules and theciliary muscle. The optic, linkage arms and connecting parts are made ofbiologically inert plastic or other biologically inert materials.

In this group of embodiments, the linkage arms are connected to pivotjoints at one or both the inner and outer ends thereof, which permit thearms to rotate about the pivot axes in response to radial expansion orcontraction of the equatorial diameter of the capsule. When the ciliarymuscle of the eye is relaxed, for distance vision, the arms hold theoptic in a position which focuses distant images onto the retina. Whenthe ciliary muscle contracts to accommodate for near vision, theequatorial diameter of the lens capsule changes, exerting force on theouter ends of the linkage arms and thereby causing them to rotate abouttheir pivots and shift the optic forward, away from the retina, so as tofocus near images onto the retina. When the ciliary muscle againrelaxes, the linkage arms move in the opposite direction, returning theoptic to its previous position of distant focus.

It may be appreciated that the equatorial diameter of the lens capsuleis determined at any time by the balance of outward radial force exertedby the zonular fibers and inward force due to the natural elasticity ofthe lens capsule. Furthermore, the portions of the lens capsuleremaining after surgery, particularly the posterior wall of the lenscapsule, provide, in some embodiments of the invention, a force which(axially) biases the optic toward the front of the eye. Furtherembodiments of the invention provide other elements for exerting forceswhich may affect the balance of forces acting on the optic and changeits axial position.

In some preferred embodiments of the present invention, the outer-endsof the linkage arms are held in contact with or attached to an expandingring, which is itself in contact with the edges of the lens capsuleadjacent to the zonules. The expanding ring serves both to hold thecapsule open (i.e., to prevent is axial collapse) and to couple thelinkage arms to the motion of the zonules. This expanding ring may alsoexert an additional outward radial force on the equatorial edge of thecapsule or may be segmented so that it provides only to position thelinkage arms and to hold the lens capsule open.

Further embodiments of the invention incorporate two or more springs orother tensile members attached at one of their respective ends to theciliary muscle, zonules or expanding ring at symmetrically spaced pointssurrounding the capsule of the eye. The other ends of the springs areeither fastened together centrally or attached to the ciliary muscle,zonules or expanding ring in such a way as to cause an inward radialforce to be exerted on the equatorial edge of the capsule. For example,such tensile members may take the form of a tensioned ring attachedalong the periphery of the lens capsule. This type of tensile membereffectively reinforces the inherent tension of the edge of the lenscapsule itself. Such tensioned members are especially useful when theposterior wall of the lens capsule is also removed.

The ciliary muscle or zonules produce a contrary force, in the outwardaxial direction. Outward radial motion of the zonules or ciliary musclewill stretch the springs, increasing the forward axial force and causingthe optic to move forward in the capsule. When the zonules or ciliarymuscle subsequently return radially inward, the linkage arms will forcethe optic back to its previous position.

In general, the lens capsule itself performs a similar function, in asomewhat different way. The elasticity of the capsule, especially whenthe capsule is held open by the expanding ring, exerts an inward forceon the edge of the lens capsule, where it is attached to the zonules.The posterior wall of the lens capsule performs an additional functionin many embodiment of the invention, in that in these embodiments theoptic is in contact with the posterior wall of the lens capsule. Underthis condition, the posterior wall acts on the optic to provide arestoring force for the optic when the diameter of the lens capsuleincreases. In this way it is not necessary to attach the outer edge ofthe haptics to the expanding ring to provide movement of the optic whenthe diameter of the lens capsule is increased.

In a preferred embodiment of the invention, in accordance withSchachar's theory of accommodation, the optic is positioned initially,for distant vision, in contact with the posterior wall of the capsule ofthe eye. Two or more linkage arms, made of rigid plastic or other rigidmaterial, are coupled flexibly to the optic so as to permit the linkagearms to pivot at the coupling during motion of the linkage arm, whilestill transmitting full axial motion from the arm to the optic. Theouter ends of the linkage arms are likewise preferably flexibly attachedto an expanding ring, which holds them in place at the edge of thecapsule adjacent to the zonules.

According to Schachar's theory, when the eye accommodates for nearvision, contraction of the zonules exerts an outward radial force, whichcauses the equatorial diameter of the lens capsule to increase.Consequent expansion of the expanding ring causes the arms to rotate intheir respective pivot joints on the expanding ring and on the optic,thereby causing the optic to move axially forward in the capsule. Thelinkage arms are geometrically constructed in such a way that a smallchange in the equatorial diameter of the capsule will cause a largerchange in optic position, sufficient to provide for focus of near imagesonto the retina.

An alternative preferred embodiment of the invention is similar to theembodiment described above, but is designed to operate in accordancewith Helmholtz's theory. In this alternate embodiment the optic iscoupled to the expanding ring by two or more linkage mechanisms, each ofwhich comprises an inner arm and an outer arm. The inner arm ispreferably rigidly connected at its inner end to the optic, and by apivot at its outer end to the inner end of the outer arm. The outer armis connected at its outer end to the expanding ring. When the ciliarymuscle contracts for near vision accommodation, according the Helmholtz,the elasticity of the lens capsule causes the capsule's equatorialdiameter to decrease and forces the expanding ring to contract. Thiscontraction causes the outer arms to rotate about their pivots in such away that the angle between the inner and outer arms at the pivotconnecting them decreases. The inner and outer arms are so arranged thatthis rotation and decrease in pivot angle will cause the optic to moveaxially forward, thus providing for near images to be focused onto theretina.

The use of rigid linkage arms or haptics differentiates the abovepreferred embodiments and other alternative embodiments of thisinvention from prior art patents cited above, such as Woods and Levy.The aforementioned patents employ deformation of flexible wire hapticsto convert radial motion of the ciliary muscle and zonules to axialmotion of the optic. Some preferred embodiments of the present inventioninclude rigid linkages, which do not substantially deform under theforces exerted by the ciliary muscle, zonules and lens capsule, andtherefore transmit motion to the optic in a more efficient and reliableway.

Other preferred embodiments of the present invention, however, may uselinkage arms or haptics made of flexible, resilient material, which maybe similar to the haptic materials used in Woods and other prior artpatents or may alternatively use rigid materials. The resilientmaterials are sufficiently stiff so that when a compressive force isapplied thereto, they do not buckle, and when the compressive force isreduced, they spring back under their own elasticity to their previousshape. Preferred embodiments of the present invention using flexible,resilient linkage arms still differ from the prior art, however, byvirtue of their use of pivot connections to convert radial motion of theciliary muscle and zonules to axial motion of the optic more efficientlyand with greater mechanical advantage.

In accordance with other preferred embodiments of the present invention,flexible, resilient linkage arms may be radially pre-loaded, for exampleby the pressure of the posterior wall of the lens capsule on the optic,so as to hold the intra-optic assembly in place without their connectionto an expanding ring.

In other preferred embodiments of the invention, the outer ends of thelinkage arms, whether rigid or flexible, may be fastened directly orindirectly to the zonules, ciliary muscle or radial edge of the lenscapsule by suturing or gluing. It may be appreciated that the varioustypes of mechanical linkages described here in relation to the variouspreferred embodiments of the invention may be used alternatively inconjunction with an expanding ring or with other methods, describedherein, of coupling the linkage arms to the motion of the zonules orciliary muscle.

In some preferred embodiments of the invention, the linkage arms orhaptics are constructed of either rigid or resilient material, and arecoupled to the edge of the capsule adjacent to the zonules, preferablyby an expanding ring. A substantially rigid ring is connected by a pivotto each of the linkage arms at a point between the arm's outer end andits inner pivot connection to the optic. The substantially rigid ringhas a diameter smaller than the minimum equatorial diameter of thecapsule, but larger than the optic and generally coaxial to it. Thepivots on the rigid ring serve as fulcrums, and the linkage arms act aslevers, rotating about the fulcrums when the capsule's equatorialdiameter changes. In accordance with Schachar's theory, the linkage armsmay be constructed so that when the equatorial diameter of the capsuleincreases, said lever action will cause the optic to move forward.

An alternative embodiment of the invention, in accordance withHelmholtz's theory, similarly includes rigid or resilient linkage arms,connected to a rigid ring with pivots acting as fulcrums for leveraction of the arms, as in the preceding embodiment. In this alternativeembodiment, however, the linkage arms are constructed so that when theequatorial diameter of the capsule decreases, said lever action willcause the optic to move forward.

In a further preferred embodiment of the invention, two optics are used,one of which is adjacent to the posterior wall of the lens capsule andthe other is held parallel and anterior to it, with an intervening spacebetween them. The refractive power of the optics and the spacing betweenthem is so designed that when the ciliary muscle is relaxed, distantobjects are focused onto the retina. Each optic is held in place by twoor more linkage arms or haptics, which are shaped and positioned in sucha way as to cause each of the arms of the anterior optic to come intocontact with and cross a corresponding arm of the posterior optic, at apivot point along or near the equatorial plane of the capsule.

These points of contact of the corresponding anterior and posteriorlinkage arms are located at a radius from the center of the capsule thatis greater than the radii of the two optics but smaller than the totalequatorial radius. The outer ends of the arms are flexibly anchored toan expanding ring at the edge of the lens capsule, adjacent to thezonules. When the ciliary muscle contracts and the equatorial diameterof the capsule decreases, in accordance with Helmholtz's theory, theangle of crossing between the corresponding anterior and posteriorlinkage arms increases in a scissors-like action, which in turnincreases the spacing distance between the anterior and posterioroptics. As this spacing increases, the laws of optics provide that therefractive power of the lens couple will decrease, thereby allowing nearobjects to be focused onto the retina. The illustrated embodimentoperates according to the Helmholtz theory. Similar embodiments,utilizing the same principles can be applied to design of lens coupleswhich operate according to the Schachar theory.

One aspect of the present invention also provides means and method forthe surgeon to adjust the focusing mechanism during or afterimplantation, so as to optimize the near and distant focus of theintraocular lens assembly. While the large range of optic motionafforded by the invention may allow the patient to achieve full near anddistant accommodation without the need for adjustment, surgicaladjustment of the focal position may improve post-operative vision incases where this full motion cannot be achieved.

For this purpose, alternative preferred embodiments of the inventionprovide for either a rigid ring, coaxial with and surrounding the optic,or the linkage arms, or both of these structures, to be formed with aplurality of kinks. A tool is provided for the purpose of straighteningthe kinks in the ring in a controlled and graduated manner, so as toincrease the diameter of the ring, causing the optic to move away fromthe capsule wall and closer to the equatorial plane of the capsule. Afurther tool is provided for straightening the kinks in the linkagearms, thereby moving the pivot fulcrum points of the linkage arms awayfrom the optic and pushing the optic farther back in the capsule. Thesurgeon may thus adjust the position of the optic when the ciliarymuscle is relaxed, so as to achieve the best focus of distant objects onthe retina. When the ciliary muscle contracts, the entire range ofmotion of the edge of the capsule adjacent to the zonules will beutilized to achieve accommodative motion of the optic within thecapsule.

There is therefore provided, in accordance with a preferred embodimentof the invention an intraocular lens assembly for implantation in ahuman eye, said eye including a ciliary muscle and zonules controlled bythe ciliary muscle, the assembly comprising:

an optic having anterior and posterior surfaces depending from a commonedge;

at least two linkage arms, each being attached to the optic at a firstposition on the arm thereof and cooperating with ciliary muscle or thezonules at a second position on the arm; and

at least two pivots, one of which is rotatably attached to eachrespective linkage arm intermediate the first and second positions.

There is further provided, in accordance with a preferred embodiment ofthe invention, an intraocular lens assembly for implantation in a humaneye, said eye including a ciliary muscle and zonules controlled by theciliary muscle, the assembly comprising:

an optic having anterior and posterior surfaces depending from a commonedge; and

at least two substantially rigid linkage arms, each being attached tothe optic at a first position on the arm thereof and cooperating withciliary muscle or the zonules at a second position on the arm.

There is further provided, in accordance with a preferred embodiment ofthe invention, for use with the intraocular lens assembly according tothe above preferred embodiments in which kinks are provided in saidlinkage arms or in an optional rigid ring, an adjustment tool forremoving said kinks, the adjustment tool comprising:

a pincer having a pair of handles and two pairs of aligned jaws oppositesaid handles rotatable about a hinge axis, for insertion into theciliary body and supporting thereon respective ones of said kinks, suchthat closing the handle presses the kinks between respective pairs ofsaid jaws thereby flattening the kinks.

There is further provided, in accordance with a preferred embodiment ofthe invention, for use with the intraocular lens assembly according tothe above preferred embodiments in which kinks are provided in saidlinkage arms or in an optional rigid ring, an adjustment tool forremoving said kinks, the adjustment tool comprising:

a pincer having a pair of handles and a pair of substantially planarsupport members opposite said handles rotatable about a hinge axis, forinsertion into the ciliary body and supporting thereon respective onesof said kinks, and

a pair of flattening members cooperating with the support members forpressing the kinks towards the support members and thereby flatteningthe kinks.

There is further provided, in accordance with a preferred embodiment ofthe invention, an intraocular lens assembly for implantation in a humaneye, said eye including a ciliary muscle and zonules controlled by theciliary muscle and at least a portion of a lens capsule including anedge thereof and at least a portion of a posterior wall thereof, theassembly comprising:

an expanding ring associated with the edge which contacts the edgeportion of the lens capsule and preferably the posterior wall andpositions the posterior wall toward the back of the eye from center ofthe lens capsule; and

an optic associated with the expanding ring.

There is further provided, in accordance with a preferred embodiment ofthe invention, an intraocular lens assembly for implantation in a humaneye, said eye including a ciliary muscle and zonules controlled by theciliary muscle and at least a portion of a lens capsule including anedge thereof, the assembly comprising:

an expanding ring associated with the edge portion of the lens capsuleand which provides a resilient radial force on the edge; and

an optic associated with the expanding ring.

Preferably, the expanding ring bears against the edge of the lenscapsule and provides an outward radial force or is attached to the edgeand provides an inward radial force.

There is further provided, in accordance with a preferred embodiment ofthe invention, an intraocular lens assembly for implantation in a humaneye, said eye including a ciliary muscle and zonules controlled by theciliary muscle and at least a portion of a lens capsule including anedge thereof and at least a portion of a posterior wall thereof, theassembly comprising:

an expanding ring associated with the edge comprising alternating rigidand elastic portions; and

an optic associated with the expanding ring.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand the invention and to see how it may becarried out in practice, some preferred embodiments will now bedescribed, by way of non-limiting example only, with reference to theaccompanying drawings, in which:

FIG. 1 shows a cross-sectional view of an eye having therein a lenscapsule containing an intraocular lens assembly according to a preferredembodiment of the invention;

FIGS. 2A and 2B are front and side views of a preferred embodiment ofthe optic shown in FIG. 1;

FIG. 3 is a front cross-sectional view of a preferred embodiment of theexpanding ring shown in FIG. 1;

FIG. 4A and 4B are front and side, partially sectioned, views of analternative preferred embodiment of the optic shown in FIG. 1;

FIG. 5 is a schematic representation of the intraocular lens assemblyaccording some aspects of the present invention, useful for explainingthe mechanical operation thereof;

FIGS. 6A and 6B are respective sectional elevations of a preferredembodiment of the invention, which operates in accordance withSchachar's theory of accommodation, showing the relative displacement ofthe optic for far vision and near vision, respectively;

FIGS. 7A and 7B are respective sectional elevations of a preferredembodiment of the invention, which operates in accordance withHelmholtz's theory of accommodation, showing the relative displacementof the optic for far vision and near vision, respectively;

FIGS. 8A and 8B are respective sectional elevations of an alternativepreferred embodiment of the invention, which operates in accordance withSchachar's theory of accommodation, showing the relative displacement ofthe optic for far vision and near vision, respectively;

FIG. 9 is a front view of a preferred embodiment of the optic shown inFIGS. 8A and 8B;

FIG. 10 is an enlarged view of a preferred embodiment of a pivotmechanism used in the embodiment of FIG. 9;

FIGS. 11A and 11B are respective sectional elevations of a preferredembodiment of the invention, which operates in accordance withHelmholtz's theory of accommodation, showing the relative displacementof the optic for far vision and near vision, respectively;

FIG. 12 is a half-sectional elevation of a modified intraocular lensassembly comprising two optics;

FIG. 13 is a front elevation of a modified, adjustable optic having morethan two fulcrums and associated levers;

FIG. 14 is a pictorial representation of a first adjustment tool for usewhen implanting the intraocular lens assembly according to theinvention; and

FIG. 15 is a pictorial representation of a second adjustment tool foruse when implanting the intraocular lens assembly according to theinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a cross-section of a human eye 10 having an adaptiveintra-ocular lens system 12, in accordance with a preferred embodimentof the invention, installed in place of the original material in a lenscapsule 16. In this and all other cross-sectional diagrams of the eyeand structures therein, the cornea and other anterior portions of theeye are at the left of the figure, and the retina and posterior portionsof the eye are to the right. Intraocular lens system 12 comprises anoptic 14 placed within lens capsule 16. Lens capsule 16, from which theoriginal lens material has been removed, includes an outer edge 19,which is left intact and, optionally, a posterior wall 18 at least aportion of which may be left intact. At least a portion of the originalanterior wall of the capsule is generally removed during the operationfor removal of the lens material leaving an opening 20, through whichthe lens system is installed.

As shown more clearly in FIGS. 2A, 2B, and 3, lens system 20 alsoincludes two or more linkage arms 22, also known as haptics, which areattached to the optic 14 at one end of the arms and which preferablyrest on or are pivotably attached to an expanding ring 24 at a secondend thereof. In a preferred embodiment of the invention shown in FIGS.1-3, arms 22 are pivotably attached for limited rotational motion atpivots 26, symmetrically placed on the outer edge of the optic 14, andat pivots 27 on expanding ring 24.

As shown in FIG. 1, one end of zonular fibers 28, also known as zonules,is attached to edge 19 of lens capsule 16. The other end of the zonulesis attached to the sclera 30 of the eye. Intermediate their ends, thezonular fibers are acted upon by ligaments or the like 32 which arecontrolled by ciliary muscle 34. The portion of the eye comprising theciliary muscle and the volume it encloses is also known as the ciliarybody.

Optic 14 produces an image on the retina at the back of the eye 10corresponding to a focal plane 36. In order to provide accommodation,optic 14 is made capable of movement along optical axis 38. As in thenormal eye, accommodation is made consequent to changes in tension ofthe zonular fibers. This change in tension acts on optic 14 so as toalter the image distance from optic 14 to focal plane 36.

In the preferred embodiment shown in FIGS. 2A and 2B, linkage arms 22are made of a relatively rigid material and are attached to the outeredge of optic 14 at pivot 26. The pivot may be made of flexiblematerial, which allows twisting or rotation of the arms about the pivotin response to rotational force applied to the arms 22, but preventssubstantial axial motion of the arms. This flexible material may also beelastic, so that pivots 26 will exert a biasing force on arms 22, whichwill tend to return optic 14 to its original position when therotational force applied to the arms is removed. Alternatively, pivot 26may be made of rigid material with a bore through which arm 22 isinserted and fastened in such a way that the arm may rotate about theaxis of the bore, but any substantial axial motion along the axis of thebore is prevented.

Other constructions for the linkage arms 22 and for their attachment tothe optic may also be provided. In an alternative preferred embodimentshown in FIGS. 4a and 4b, rigid linkage arms 22 are pivotably attachedto the face of optic 14. Pivots 26 may in this case be constructed inthe form of an indentation 21 in the face of optic 14, which is filledwith a flexible plastic material, and in which the end of linkage arm 22is embedded. In this manner, the angle between linkage arm 22 and theoptical axis 38 of optic 14 may change in response to radial forcesexerted on the linkage arm, due to flexing of pivot 26. Alternatively oradditionally, portions of the haptics which are adjacent to 26 are alsomade flexible.

Within the context of the invention the terms "rigid" and "flexible" or"resilient" have a special meaning. The haptics attached to the optic inprior art, such as in the Woods patent, to which reference has beenmade, are, in fact, resilient wires formed of plastics or any otherbiologically inert material. They are sufficiently stiff so that when acompressive force is applied thereto, they distort but do not buckle.Rather, they push the optic to which they are attached forward along theoptical axis. However, they are also sufficiently resilient so that whenthe compressive force is reduced, they spring back under their ownelasticity so as to return the optic toward its original position. It isthis property, namely that a compressive force applied to the lever armsdoes not cause them to buckle or otherwise collapse, which is essentialfor prior art inventions, and it is to this extent that the term"flexible, resilient" is to be understood herein.

Many preferred embodiments of the present invention, however, usesubstantially rigid elements, and in particular substantially rigidlinkage arms or haptics. These elements are considered to be rigidbecause, in these embodiments, they do not deform significantly underthe compressive or tensile forces present during accommodation. Theyare, therefore, capable of transmitting forces applied to them moreefficiently than flexible elements and potentially with greatermechanical advantage. It is in this context that the term "rigid" is tobe understood in relation to the present invention. It should beunderstood, however, that these "rigid" segments are made of very thinmaterial and may not be rigid under other circumstances, such as duringsurgical implantation, when greater force is applied to them so thatthey can be inserted into the lens capsule.

Expanding ring 24 is constructed so as to exert an outward radial force,which will cause the ring to conform to the edge 19 of lens capsule 16,and expand or contract in response to expansion or contraction of thecapsule, respectively. Ring 24 serves to couple the outer end of linkagearms 22 to edge 19, so that radial forces exerted by zonules 28 andciliary muscle 34 can act upon said arms. Ring 24 may further serve toopen capsule 16, i.e., to separate the anterior and posterior portionsof the lens capsule, in place of the natural lens that was surgicallyremoved, so that the elasticity of the capsule may serve moreadvantageously to exert inward radial force on the lens assembly asdescribed below.

In a preferred embodiment, shown in FIG. 3, ring 24 comprisesalternating segments of rigid and compressible materials. Rigid segments25 ensure that ring 24 maintains its circular shape and that the capsuledoes not collapse. Compressible segments 29 exert tangential force onadjacent rigid segments, causing the ring to expand if it is notradially constrained. In the embodiment described here, radialconstraint is provided by edge 19 of the lens capsule which isconstrained from outward movement by the resilient nature of the lenscapsule.

In the preferred embodiment shown in FIG. 3, the ring includes pivots27, to which the outer ends of linkage arms 22 are attached. Suchattachment may be made at the time of manufacture of assembly 12, andpivots 27 may be similar in construction to pivots 26 on the optic, asdescribed above. In an alternative embodiment, expanding ring 24 ismanufactured separately from optic 14 and linkage arms 22. Expandingring 24 may then be implanted in capsule 16 by the surgeon. The surgeonmay next position the optic and insert the linkage arms into receptacleson the expanding ring, such receptacles being produced in such a way asto permit the ends of the linkage arms to be pressed or snapped intothem and held thereby, so that the linkage arms may pivot about theiraxes while remaining permanently fixed therein. Such a receptacle isshown for example in FIG. 10.

In another alternative embodiment thereof, expanding ring 24 may beprovided without pivots. The outer ends of linkage arms 22 bear againstthe inner surface of expanding ring 24, but are not fastened thereto,and are thus free to rotate about their own axes.

In a further alternative embodiment, expanding ring 24 may beeliminated, and linkage arms 22 may instead be rotatably coupled attheir outer ends to anchors, which may be glued or sutured to capsuleedge 19, zonules 28 or less preferably, ciliary muscle 34. Morepreferably, the expanding ring is not eliminated but is provided as asplit ring so that it exerts no force of its own in the radial directionwhile preserving the lens capsule in an open condition.

The preferred embodiments of the invention shown in FIGS. 1-4 and inFIGS. 6 through 12 will generally be described herein in terms of rigidlinkage arms 22, pivotably attached to expanding ring 24 and/or to arelatively rigid ring. It will be appreciated, however, that someembodiments of the invention may incorporate either rigid or flexible,resilient linkage arms 22. Furthermore, the linkage arms may generallybe coupled to optic 14 and to edge 19 of the capsule or zonules 28according to any of the embodiments described herein.

FIG. 5 shows a schematic representation of the intraocular lens assemblyaccording some aspects of the present invention, useful for explainingthe mechanical operation thereof and in particular in illustrating theaction of the forces that operate on intraocular lens system 12, duringaccommodative motion of optic 14. The embodiment of the presentinvention that is shown in FIGS. 1-4 may be considered to be onepreferred embodiment of the more general scheme shown here in FIG. 5.

While FIG. 5 generally follows Schachar's theory of accommodation, itshould be understood that the principles of the present inventions areequally applicable to the Helmholtz theory of accommodation, as will beshown in some of the examples described below.

In FIG. 5, the posterior wall 18 of the lens capsule contacts the rearsurface of optic 14. The resilience of the posterior wall is indicatedby springs to indicate that the resilient wall biases the optic to theleft, i.e., to the front of the eye. An optional tensive element 96 maybe further provided between the ends 19 of the lens capsule as describedabove. Additionally, the edge of the lens capsule also acts as a tensiveelement 96. In addition the expanding ring, not shown in FIG. 5, forsimplicity, may be present and may partially counteract the effect ofthe posterior wall and tensive element 96.

One way of providing tensile elements 96 is to attach an elastic ring,which is preferably in tension during both far and near vision, to thezonules or to the edge of the lens capsule. This attachment may be bysuturing the elastic ring to the edge of the lens capsule. Preferably,when such tensive action is required, as for example, when the posteriorwall is removed, the expander ring is made tensive, in use, rather thanbeing in compression as described above. Such a ring would be implantedby expanding the ring utilizing a removable expanding ring, suturing thering to the edge of the lens capsule and then removing the expansionring. This type of tensile member effectively reinforces the inherenttension of the edge of the lens capsule itself.

The edge of the lens capsule is connected to springs 100 which representthe effect of the zonules.

At least two linkage arms 104 are connected to opposing the edges ofoptic 14 where they are rotatable about pivots 106. The correspondingouter positions on arms 104 bear against the ends 19 of the lenscapsule. where they pivot at pivot points 107. As described above, inpreferred embodiments of the invention an expanding ring 24 mayintervene between arms 104 and zonules 100, although arms 104 may alsobe secured to the zonules by gluing or suturing. For the sake ofsimplicity, these elements are not shown in FIG. 5. Furthermore,although arms 104 are shown having substantially the form of theembodiment of FIGS. 1-4, they may have the forms shown below in theother embodiments of the invention, as appropriate.

The outward radial tension which is applied to lens capsule edge 19 byzonules 100, which tension may be considered to include, as well,outward radial force exerted by expanding ring 24 in some preferredembodiments of the invention.

In general, the axial position of the optic depends on the balance offorces between the zonules 100 (and the expanding ring, if present)which urge edge 19 of the lens capsule outward and the resilience of thelens capsule (and tensile element 96, if present) which urges the edgeof the lens capsule inward. The effect of the force of the posteriorwall 18 of the lens capsule on the optic also tends to push edge 19 ofthe lens capsule, outward. In many embodiments of the invention theurging of the optic by the posterior wall enables the expanding ring 24and the outer end position on the linkage arms to be held in placewithout any attachment of the lens assembly to the lens capsule or tothe zonules. This simplifies implantation considerably.

In the arrangement shown in FIG. 5, increased outward radial force onzonules 100, generally due to contraction of the ciliary muscle, inducesoutward motion of edge 19. This motion results in a net radial movementof the outer ends of linkage arms 104, whereby tension in the posteriorwall (and tensile element 96, if present) is increased. This will causelens 14 to move forward (to the left), until a new balance of forces isreached.

When the radial force on zonules 100 is reduced, edge 19 moves backinward, which would cause a reduction of the tension in the posteriorwall in the absence of optic 14. However, this reduction in tension isat lease partially mitigated by pressure from the optic which is forcedagainst the posterior wall by the inward movement of the outer edge ofarms 104.

It may be appreciated that in preferred embodiments of the presentinvention, a wide variety of mechanical designs may be applied to theintraocular lens system and, more specifically, to linkage arms 104 andpivots 106 and 107, with the objective of increasing and otherwisecontrolling the axial displacement of optic 14 resulting from radialforces applied at pivots 107. Preferably, the ratio of axial to radialdisplacement is large enough to provide at least 5:1 amplification ofthe radial motion, so as to provide substantially completeaccommodation. In saying this, it is understood that completeaccommodation requires an axial movement of the optic 14 ofapproximately 1 mm whilst the maximum radial movement of the ciliarymuscle 34 is approximately 200 micrometers. However, it will beappreciated that other ratios may be employed as required. Inparticular, a larger ratio will result in a range of accommodation whichis larger than required for near/far vision. When such largeraccommodation ratios are available, the exact placement of the opticbecomes less critical since the contraction of the ciliary muscle willbe sufficient to provide full accommodation even if far vision isovercompensated when the ciliary muscle is relaxed.

FIGS. 6A and 6B are partial cross-sections showing a detail of apreferred embodiment of the intraocular lens assembly 12 depicted inFIG. 1 and showing more clearly the construction and operation of thelinkage arm 22 and pivots 26 and 27. Linkage arms 22 are characterizedby a radial reach and axial reach. Radial reach is defined herein as thesum of the respective radial distances of pivots 26 and 27 from theoptical axis. Axial reach is defined as the difference between therelative axial positions of these pivots. Because the radial reach oflinkage arm 22 is greater than the axial reach, a small radial movementapplied to the outer end of arm 22 gives rise to a correspondinglygreater axial movement of the inner end to which the optic 14 isattached.

In operation, in response to changes in the tension of the zonularfibers 28, edge 19 of lens capsule 16, which is adjacent to the fibers,moves radially in and out. This radial movement causes force to beexerted on arms 22, thereby causing the arms to rotate about pivots 26and 27. It will be appreciated that outward motion of the edge 19 of thelens capsule 16 will cause the outer end of arm 22, which is attached tothe expanding ring 24, to move radially away from the optical axis 38,and the inner end of arm 22 will then-move axially forward, away fromthe focal plane 36 of the eye.

In FIG. 6A, the zonular fibers 28 are at their maximal extension,corresponding, in accordance with Schachar's hypothesis, toaccommodation of the eye for distant vision. In this case optic 14presses against the posterior wall 18 of the capsule, at such distancefrom focal plane 36 as to create a focused image at the focal plane ofobjects distant from the eye. In FIG. 6B, where accommodation of the eyefor near vision is shown, zonular fibers 28 have contracted, pullingedge 19 of the capsule outwards, and causing linkage arms 22 to rotateabout pivots 26 and 27, so that optic 14 moves to the left, away fromthe retina, to such distance from the focal plane 36 as to create afocused image at the focal plane of objects near the eye. In theconfiguration shown in FIGS. 6A and 6B, pressure of posterior wall 18 ofcapsule 16 may exert a forward resilient biasing force on optic 14 whichmoves the optic to the left when the tension in the zonules increases,as described above.

When the eye returns to distant vision accommodation, zonular fibers 28extend, causing outer edge 19 of the capsule to contract due to inwardradial force exerted by the elastic capsule. As a result of thiscontraction, linkage arms 22 will rotate back to the position shown inFIG. 6A and will return optic 14 to its distant focus position.

As noted above, in the preferred embodiment of the invention describedwith reference to FIGS. 6A and 6B, an expanding ring 24 with pivots 27is used to couple linkage arms 22 to the edge of the capsule 19 andzonules 28, and to exert an outward radial biasing force. Pivots 26 areprovided to connect arms 22 to the edges of optic 14. Further asdescribed above with respect to FIG. 5, capsule wall 18 exerts an inwardradial force on the edge 19 of the capsule and a forward biasing forceon the optic. We note, however, that the mechanical principles operativein the embodiment shown in FIGS. 6A and 6B could more generally beapplied to alternative preferred embodiments of the invention, utilizingother types of linkage arms, pivots and couplings, as are describedhereinabove. These alternative elements could similarly be used in thepreferred embodiments of the invention to be described below.

FIGS. 7A and 7B show another preferred embodiment of the invention thatoperates under the Helmholtz theory of accommodation. In this case, itwill be appreciated that when the eye accommodates for near vision,zonular fibers 28 relax, causing edge 19 of the capsule to move inward.In this embodiment, optic 14 is connected to expanding ring 24 by a pairof articulated linkages 50. Each linkage comprises an outer arm 52 andan inner arm 54, connected together by a pivot joint 56. Outer arm 52 isattached to the expanding ring 24 by a pivot 48, which permits thelinkage to rotate in the plane of the cross section. Inner arm 54 isfixed rigidly to optic 14 at point 51.

When the eye accommodates for distant vision, optic 14 rests againstposterior wall 18 of the capsule at a distance at which a focused imageof distant objects is formed on the retina. When the eye accommodatesfor near vision, edge 19 of the capsule moves inward, causing pivot 48to move radially inward and outer arm 52 to rotate clockwise about pivot48. Pivot 56 moves forward, to the left as shown in FIG. 7B, causingoptic 14 to be drawn forward to a position farther from the retina, thusallowing focused images of objects near the eye to be formed on theretina. In this embodiment of the invention, outer arm 52 must bepivotably attached to ring 24 which is also preferably attached to orbiased against edge 19 of the lens capsule. In this way the motion ofedge 19 is reliably transmitted to outer arm 52.

In another preferred embodiment of the invention, shown in FIGS. 8A and8B, and described herein in reference to Schachar's theory ofaccommodation, the linkage arms may be configured as levers, so as tofurther amplify the radial motion of capsule edge 19. A rigid ring 55,whose diameter is larger than that of the useful area of the optic butsmaller than the minimum equatorial diameter of the lens capsule, isconnected to the linkage arms by pivots 57, and which are positioned tohold ring 55 coaxial with optic 14.

Ring 55 is shown in front view in FIG. 9, together with optic 14 andlinkage arms 22. FIG. 10 shows a detail of the construction of apreferred embodiment of linkage arm 22, ring 55 and pivot 57 shown inFIG. 9. Ring 55 has at least two sections 67 and 69, which areinterconnected by a biologically inert elastic sleeve 31 which fits overthe junction of the two sections 67 and 69 so as to leave a small gap 33therebetween which, owing to the elasticity of the inert sleeve, allowstwisting of the adjacent sections 67 and 69 of the pivot 57. The portionof the inert sleeve 33 intermediate the two sections 67 and 69 of thering 22 is anchored to the linkage arm 22 so that, consequent toapplication of radially directed force to the outer section of the arm22, the sleeve 33 twists, thereby allowing rotation of the arm aboutpivot 57. By means of this construction, the natural tendency of thebiological tissue to grow around the inert sleeve 33 owing to attemptedrejection by the body of the intraocular implant, which constitutesforeign matter, does not impede the performance of pivot 57.

The pivot embodiment described here in reference to pivot 57 on ring 55,based on a flexible sleeve or other flexible element coupling two rigidelements, may also be useful in other pivots used in other preferredembodiments of the invention, such as pivot 56, shown in FIGS. 7A and7B, and pivot 59 in FIGS. 8A and 8B.

Referring again to FIGS. 8A and 8B, it may be seen that when zonules 28draw the edge 19 of the capsule radially outwards, as the eyeaccommodates for near vision, arms 22 will act as levers, rotating aboutpivots 57, which serve as fulcrums. Linkage arms 22 further pivot atpivot connections 26 and 27, to the optic 14 and expanding ring 24respectively, and flex at joint 59. Thus, the inner portions 42 of thelinkage arms 22, will pull the optic 14 axially forward. The mechanicaladvantage of the levers, due to the inner lever arm 42 beingsubstantially longer than outer lever arm 40, will amplify small radialmovements of the edge of the lens capsule 28 into larger axial movementsof optic 14.

FIGS. 11A and 11B show a cross-sectional view of another preferredembodiment of the invention, operable under the Helmholtz theory ofaccommodation. This embodiment is similar to the preceding one, usinglinkage arms 22 as levers, with pivots 57 on rigid ring 55 serving asfulcrums. In the present embodiment, however, linkage arms 22 are soconfigured that when accommodation of the eye for near vision causes theedge 19 of the capsule to move radially inward, linkage arm 22 willrotate about pivot 57 in such a way as to cause optic 14 to move axiallyto the left, away from the retina, as required for near accommodation.Preferably, at least portions 59 and, optionally, 61 of arm 22 areflexible to allow the arm to rotate about pivot 57. Furthermore, pivot26 is provided between the arm and the optic as described above.

It may be appreciated that other preferred embodiments of the presentinvention may use linkage arms 22 that are formed of flexible, resilientmaterial, as discussed earlier, with or without expanding ring 24. Rigidring 55 is still provided, with pivots 57 to act as fulcrums for thelever action of arms 22. In these embodiments, the resilient arms 22 aremechanically pre-loaded and hold the optic 14 in place by pressure oftheir outer ends against the edges 19 of the capsule. Such embodimentsstill utilize the same mechanical leverage principles as the precedingembodiments, which are based on rigid linkage arms.

FIG. 12 shows, in cross-section, another embodiment of the inventionwherein a lens doublet comprising a pair of optics 58 and 60 areemployed, commonly connected by respective linkage arms 62 and 64,commonly hinged to a pivot 66 and anchored to a peripheral expandingring 24 within the lens capsule 16. The various embodiments describedearlier with reference to the flexibility or rigidity of the linkagearms, the methods of mounting them to the optics and the methods ofcoupling them to the motion of the zonules, also apply to the lensdoublet shown in FIG. 12. Optics 58 and 60 and the distance between themare chosen so that when the zonules are relaxed, the refractive power ofthe lens doublet is such as will cause focused images of distant objectsto be formed on the retina.

In the arrangement shown in FIG. 12, following Helmholtz's theory ofaccommodation, contraction of the ciliary muscle results in an inwardlydirected radial force being applied to lever arms 62 and 64, resultingin mutual counter-rotation thereof whereby optics 58 and 60 are pushedfarther away from each other. As explained by Sarfarazi in U.S. Pat. No.5,275,623, is incorporated herein by reference, increasing the distancebetween optics 58 and 60 will decrease the refractive power of the lensdoublet, thereby causing objects nearer the eye to form focused imageson the retina, so that when the ciliary muscle contracts, the eye isaccommodated for near vision.

The actual focal length of optic 14 which is to be implanted within thelens capsule 16 is a function of the size of the eyeball and refraction(myopia or hyperopia) of the eye, among other things, and will vary frompatient to patient. An advantage of the present invention is that themechanism it provides for accommodative movement of optic 14 withincapsule 16 causes the small radial motion of the edge 19 of capsule wallto be amplified into a relatively larger axial motion of the optic. Thislarge accommodative movement enables the eye to achieve a full range ofaccommodation, from distant to near vision, and can compensate fordifferences in the sizes of the eyeball and refraction from patient topatient.

For some patients, however, it may be desirable to provide for positionadjustment within lens capsule 16, so that optic 14 will be located at asuitable distance from the center of the lens capsule, such that whenthe ciliary muscle is completely relaxed, the eye is correctly focusedon infinity, this being the correct adjustment for far vision. Inpractice, it is very difficult to position the optic precisely duringthe implantation surgically without a certain amount of trial and error,and therefore means are preferably provided for allowing smalladjustments to be made to the axial displacement of optic 14. However,it is possible to measure the refraction of the lens in situ using, forexample, a refractometer, and to correct the refraction as outlinedbelow.

This adjustment may be accomplished by means of two alternativeembodiments of the invention, which are operable either separately ortogether, both of which are shown schematically in FIG. 13. The firstalternative embodiment, which allows adjustment of optic 14 towardposterior wall 18, makes use of a ring 70, which is formed with aplurality of kinks 72. These kinks may be straightened out duringsurgery so as to increase the effective diameter of the ring 70 andproduce an outwardly directed radial force on linkage arms 74, whereuponthere results a net movement of optic 14 toward the posterior wall.

FIG. 14 shows, pictorially, an adjustment tool 76 for removing, eithercompletely or partially, kinks 72 from ring 70. Adjustment tool 76 is inthe form of a pincer having a pair of handles 78 and a pair ofsubstantially planar support members 80 opposite the handles androtatable about a hinge axis 82. Adjustment tool 76 is inserted into thelens capsule so as to support kinks 72 on respective ones of the supportmembers 80. Adjustment tool 76 also includes a pair of flatteningmembers shown schematically as 84 which cooperate with support members80 for pressing on ring 70 so that kinks 72 are flattened by flatteningmembers 84 bearing down on support members 80.

Referring again to FIG. 13, it will be seen that as a second way ofadjusting the lateral position of optic 14 in the capsule, levers 74 arealso provided with two kinks 75. These kinks may be at least partiallystraightened using a specially designed pincer, thereby effectivelylengthening the respective levers and causing a net axial movement ofthe optic 14 in a posterior direction toward the focal plane.

Referring now to FIG. 15, a specially designed pincer for straighteningout simultaneously both kinks 75 will be described. A pincer showngenerally as 86 includes a head portion 88 having two upper aligned jaws90 and two lower aligned jaws 92. In use, the two kinks 75 in the levers74 are respectively aligned between the two pairs of jaws such thatclosing the jaws by means of a handle 94 flattens kinks 75, and causesthe desired axial movement of the optic 14 in a posterior directiontoward the focal plane.

As has been explained above, a resilient biasing force may convenientlybe provided by the natural elasticity of the posterior capsule wall 18and the edge of the lens capsule 19. In this case, for those embodimentsof the invention which require the restoring force of the posterior wallon the optic, the position of the optic 14 within the lens capsule 16must be adjusted so that, for correct far vision when the ciliary muscleis completely relaxed, the rear surface of the optic 14 contacts theposterior capsule wall 18. This too can be provided by the methodologydescribed with respect to FIGS. 13-15.

In the preferred embodiments described hereinabove, lens assembly 12 ismounted completely within lens capsule 16 and an inward radial resilientbiasing force is provided by the inherent elasticity of remainingportions of the lens capsule. However, the lens capsule may be dispensedwith for some of these embodiments by providing auxiliary springs whichact as tensile elements 96, as shown in FIGS. 5, so as restore the opticto its equilibrium position on relaxation of the ciliary muscle, and byattaching or anchoring the lever arms to the ciliary muscle or zonules.The inward radial biasing force may comprise, for example, a tensionedring attached to the zonules or to the ciliary muscle itself.

The present invention has been. described, generally, for lens implantsutilizing rigid optics. Alternative preferred embodiments of the abovedescribed embodiments of the invention utilize soft optics which mayhave a number of advantages over rigid optics. Firstly, the soft opticsmay be folded during implantation, such that the opening in the anteriorwall of the lens capsule may be reduced. Secondly, some of the joints,for example, those which provide flexible joints at the juncture of thelinkage arms and the optic or between the fulcrum and the optic, may bedispensed with and their function assumed by a slight bending of theedges of the optic itself.

In general, the materials used in the present invention are similar tothose used in the prior art and include nylon and proline for theresilient linkage arms and the flexible elements, polymethylmethacrylate(PMMA) or hydrogel for the rigid optic and silicone for the soft optic.Preferably the rigid linkage arms and other rigid elements are formed ofstainless steel wire optionally covered by proline or nylon or otherinert material. The surface of all or part of the lens system may becovered with Haperin or other biologically active compound to reducebody rejection of the lens system.

It is to be understood that, during cataract operations, at least partof the anterior capsule wall is usually destroyed and part of theposterior capsule wall may also be damaged. Therefore, the term"posterior capsule wall" as used in the specification and claims embracealso partial capsule walls as appropriate.

I claim:
 1. An intraocular lens assembly for implantation in a humaneye, said eye including at least a portion of a lens capsule, a ciliarymuscle and zonules controlled by the ciliary muscle, the assemblycomprising:an optic having anterior and posterior surfaces; an at leastpartial ring adapted to cooperate with the ciliary muscle or thezonules; and at least two linkage elements, each being pivotablyattached to the optic at a first position on the element and beingpivotably attached to the at least partial ring at a second position onthe element to cause axial movement of the optic in response to movementof the ciliary muscle or the zonules; and also comprising a generallyrigid ring having a diameter greater than that of the optic and lessthan that of said at least partial ring and wherein the linkage elementsare pivotably attached at locations intermediate the ends of the linkageelements onto said rigid ring at pivots located on said rigid ring. 2.An intraocular lens assembly according to claim 1 wherein the pivotscomprise flexible portions in said otherwise rigid ring.
 3. Anintraocular lens assembly according to claim 2, wherein:the rigid ringis formed of at least two rigid sections interconnected by abiologically inert sleeve so as to allow twisting of respective portionsof the sleeve intermediate the rigid sections, and said respectiveportions of the sleeve serve as fulcrums.
 4. An intraocular lensassembly according to claim 3, wherein said rigid ring is provided withone or more initial kinks which can be at least partially straightenedduring implantation of the lens assembly in order to adjust the distanceof the optic from the rear surface of the eye.
 5. An intraocular lensassembly according to claim 3, wherein at least two optics are commonlycoupled to the respective linkage elements.
 6. An intraocular lensassembly according to claim 4, wherein at least two optics are commonlycoupled to the respective linkage elements.
 7. An intraocular lensassembly according to claim 2, wherein said rigid is provided with oneor more initial kinks which can be at least partially straightenedduring implantation of the lens assembly in order to adjust the distanceof the optic from the rear surface of the eye.
 8. An intraocular lensassembly according to claim 7, wherein at least two optics are commonlycoupled to the respective linkage elements.
 9. An intraocular lensassembly according to claim 2, wherein at least two optics are commonlycoupled to the respective linkage elements.
 10. An intraocular lensassembly according to claim 1, wherein at least two optics are commonlycoupled to the respective linkage elements.
 11. An intraocular lensassembly for implantation in a human eye, said eye including at least aportion of a lens capsule, a ciliary muscle and zonules controlled bythe ciliary muscle, the assembly comprising:an optic having anterior andposterior surfaces; an at least partial ring adapted to cooperate withthe ciliary muscle or the zonules; and at least two linkage elements,each being pivotably attached to the optic at a first position on theelement and being pivotably attached to the at least partial ring at asecond position on the element to cause axial movement of the optic inresponse to movement of the ciliary muscle or the zonules;wherein eachof said linkage elements is adapted to apply a resilient bias tomaintain the optic at a desired distance from the rear surface of theeye; and wherein the at least a portion of a lens capsule includes atleast a peripheral edge thereof attached to the zonules and wherein theresilient bias is at least partially applied to the edge; and whereinthe lens capsule also includes at least a portion of a posterior wallthereof and wherein the resilient bias is at least partially applied tothe posterior wall; and wherein said at least partial ring comprises anexpanding ring associated with the edge which is adapted to contact theedge of the lens capsule and position the posterior wall toward the backof the eye and away from the center of the lens capsule.
 12. Anintraocular lens assembly for implantation in a human eye, said eyeincluding at least a portion of a lens capsule, a ciliary muscle andzonules controlled by the ciliary muscle, the assembly comprising:anoptic having anterior and posterior surfaces; an at least partial ringadapted to cooperate with the ciliary muscle or the zonules; and atleast two linkage elements, each being pivotably attached to the opticat a first position on the element and being pivotably attached to theat least partial ring at a second position on the element to cause axialmovement of the optic in response to movement of the ciliary muscle orthe zonules;wherein each of said linkage elements is adapted to apply aresilient bias to maintain the optic at a desired distance from the rearsurface of the eye; and wherein the at least a portion of a lens capsuleincludes at least a peripheral edge thereof attached to the zonules andwherein the resilient bias is at least partially applied to the edge;and wherein the lens capsule also includes at least a portion of aposterior wall thereof and wherein the resilient bias is at leastpartially applied of the posterior wall; and wherein the resilient biasis at least partially applied by stretching of the posterior capsulewall attached to the ciliary muscle at opposing extremities of the lenscapsule; and wherein said at least partial ring comprises an expandingring associated with the edge which is adapted to contact the edge ofthe lens capsule and position the posterior wall toward the back of theeye and away from the center of the lens capsule.
 13. An intraocularlens assembly according to claim 12 wherein the rigid ring is formed ofalternating rigid and elastic portions.
 14. An intraocular lens assemblyfor implantation in a human eye, said eye including at least a portionof a lens capsule, a ciliary muscle and zonules controlled by theciliary muscle, the assembly comprising:an optic having anterior andposterior surfaces; an at least partial ring adapted to cooperate withthe ciliary muscle or the zonules; and at least two linkage elements,each being pivotably attached to the optic at a first position on theelement and being pivotably attached to the at least partial ring at asecond position on the element to cause axial movement of the optic inresponse to movement of the ciliary muscle or the zonules;wherein atleast a portion of the linkage elements are provided with one or moreinitial links which can be at least partially straightened duringimplantation of the lens assembly in order to adjust the distance of theoptic from a rear surface of the eye.